1. Field of the Invention
The invention relates to a family of devices which use image intensifier tubes. Early versions of these tubes used electron optics between a photocathode and a phosphor screen anode to produce intense images of objects at extremely low ambient light levels. The electron optics are now being replaced with thin microchannel plates which greatly reduce the size and weight of the tubes and provide other advantages as well.
2. Description of the Prior Art
To test the above devices rigid standards have been adopted and sophisticated test equipment has been evolved. This insures that only devices in top working condition are issued to the field, at least in military situations. Once the devices are in field use the situation is quite different. The degradation of performance of the devices can be quite subtle. An operator in the field may be unable or unwilling to accept that such degradation has taken place, for a variety of reasons and could thereby compromise an important mission. In order to improve this situation applicant devised a field test unit for a variety of intensifier devices which could be used in the field. This tester is disclosed in patent application Ser. No. 818,264 for a "VISIBLE IMAGE PERFORMANCE MONITOR," filed July 22, 1977. It utilizes a diffusing device disclosed in U.S. Pat. No. 4,149,228 issued Apr. 10, 1979 for a "COMPACT UNIFORM LIGHT DIFFUSER AND ATTENUATOR." This tester is ideal for ground units which use a variety of intensifier devices concentrated in a fairly small region. Exceptions to this are the devices used by airborne units and some motorized ground units. Popular devices used by both are the AN/PVS-5 goggles. A set of goggles comprises a mounting frame and two demountable oculars, each ocular having an objective lens, an image intensifier and an eyepiece in a tubular ocular housing. They are mounted on the headgear of the user and become dispersed over wide areas and in inaccessible places. Used in night flying and driving, they are probably much more critical than other devices on a moment by moment basis and receive greater useage. The tester described above is too cumbersome and expensive to be used in such service.